(341c) Development of a Novel Process and Physico-Chemical Data for the Production of Crotonaldehyde From Aqueous Acetaldehyde Solutions
Crotonaldehyde is an important intermediate in several value added chains in the chemical industry, e.g. in the production of sorbic acid. The state-of-the-art process for the production of Crotonaldehyde is described in . The starting material is Acetaldehyde in aqueous solution. It is converted in a two-step process, first under basic and then under acidic conditions, to Crotonaldehyde following an Aldol addition-condensation mechanism. Several intermediates occur, with Acetaldol being described as the most important. There are also side reactions. The information which is available in the literature is not sufficient to set up a reliable model of the process or to study alternatives.
Therefore, in the present work, in a first step, fundamental studies on the reaction system involved in the Crotonaldehyde production from Acetaldehyde were carried out using NMR spectroscopy. Surprisingly, it was found that Acetaldol is only present in small quantities. The reaction mechanism was elucidated and a quantitative model of the reaction network was developed. The proposed model also takes into account that Acetaldehyde reacts with water and forms oligomers. Despite the industrial importance of aqueous solutions of Acetaldehyde, the information available in literature on the chemistry in that system is poor. That gap was closed by further systematic NMR spectroscopic studies, and a new physico-chemical model for describing the vapor-liquid equilibrium of aqueous solutions of Acetaldehyde was developed based on the experimental results.
The new models were used for developing a novel highly integrated process for the production of Crotonaldehyde from aqueous solutions of Actetaldehyde which is advantageous in comparison with the established process described in .
 R. Schulz et al.: Crotonaldehyde and Crotonic Acid, in: Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005, 1-8